In recent years, chargeable/dischargeable secondary batteries are being widely used for energy sources or auxiliary power devices of wireless mobile equipment. Also, secondary batteries have attracted considerable attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), which have been developed to solve limitations, such as air pollution, caused by existing gasoline and diesel vehicles that use fossil fuels.
Such a secondary battery is manufactured in the form in which an electrode assembly together with an electrolyte is provided in a battery case. The electrode assembly may be classified into a stacked type electrode assembly, a folding type electrode assembly, and a stack and folding type electrode assembly. In case of the stacked type or stack and folding type electrode assembly, a unit assembly has a structure in which a cathode and an anode are successively stacked with a separator therebetween. In order to manufacture the unit assembly, a laminating process for bonding the electrode to the separator is necessary.
In general, the laminating process includes a process of heating the unit assembly to bond the electrode to the separator. An indirect heating method using radiation and convection is mainly used as a method for the heating of the unit assembly. Since processes of manufacturing the secondary battery are organically connected to realize mass production, the foregoing method is for laminating the unit assembly while transferring the unit assembly.
However, in the indirect heating method using the radiation and the convection, it takes a long time to rise a temperature of the unit assembly up to a target temperature when compared to a direct heating method in which heat is transferred through direct contact.
To solve this limitation, a secondary battery laminating device using contact-type heating has been developed.
FIG. 1 is a schematic view illustrating an example of a secondary battery laminating device according to the related art, and FIG. 2 is a view illustrating a pressure applied to an electrode assembly of the secondary battery laminating device according to the related art.
However, as illustrated in FIGS. 1 and 2, in case of the secondary battery laminating device 200 according to the related art, even though an electrode assembly 10 varies in thickness in a width direction of a separator, a bonding part 220 having a flat contact surface is used without considering a variation in thickness of the electrode assembly 10. Thus, defects in overall bonding force may occur.
That is, when the secondary battery laminating device 200 having the bonding part 220 with the flat structure according to the related art is used, although an electrode 11 of the electrode assembly 10 is bonded to a separator 20, since bonding between an electrode tab 12 and the separator 20 does not occur, uniform bonding may not generally occur to deteriorate the bonding force.